Effects of PNF Stretching on Flexibility in Adults with Hamstring Tightness: A Systematic Review

Purpose: This systematic review synthesized randomized controlled trial (RCT) evidence on the effects of proprioceptive neuromuscular facilitation (PNF) stretching on hamstring flexibility in adults with hamstring tightness. Methods: PubMed, Embase, CINAHL, SPORTDiscus, and Web of Science were searched for RCTs published from January 2016 to January 2026. Eligible studies included adults with hamstring tightness who received PNF hold–relax or contract–relax stretching. Comparators were static stretching, no intervention, abdominal hypopressive technique (AHT), instrument-assisted soft tissue mobilization (IASTM), or conventional physical therapy. Outcomes included straight leg raise (SLR), active knee extension test (AKET), chair sit-and-reach test (CART), and toe–floor distance (TFD). Risk of bias was assessed using the Cochrane tool. Results: Three RCTs (n=106) were included. Over 4 weeks, PNF contract–relax improved knee extension range of motion and biceps femoris electromyographic activity more than static stretching or control in older adults. In adults with shortened hamstrings, a single PNF session improved SLR and TFD, but did not differ significantly from AHT. In patients with knee osteoarthritis, IASTM produced greater improvements in AKET and pain/function outcomes than PNF. Blinding was limited, and attrition imbalance was noted in one trial. Conclusion: PNF stretching may improve hamstring flexibility compared with static stretching or no intervention; however, evidence is limited and heterogeneous, and superiority over other active interventions is inconsistent. Future trials should standardize PNF dosage and examine long-term effects.